Q beta replicase is a four-subunit enzyme induced after Q beta bacteriophage infection of Escherichia coli. Its function is to replicate the single-stranded Q beta RNA. Three of the subunits are host-coded and are normally involved in protein biosynthesis in uninfected E. coli. Two of these, protein synthesis elongation factors EF-Tu and EF-Ts, act as a complex in Q beta replicase. They do not perform their known protein synthetic functions in the RNA-dependent RNA synthesis reaction. Our research is designed to determine whether they are mimicing an unknown host function for the EF-Tu.Ts complex or whether they are performing an entirely new function in the Q beta replicase reaction. To this end we are studying interactions between this complex and other cellular components; quantitating the complex and separate elongation factors under varying cell conditions; and performing a variety of physical and chemical studies on the complete Q beta replicase to determine the nature of the physical association between the EF-Tu.Ts and the other enzyme subunits. Other projects include the isolation of mitochondrial elongation factor T from yeast and the determination of the normal function of a fifth host-coded polypeptide involved in Q beta RNA replication, "host factor". BIBLIOGRAPHIC REFERENCES: Blumenthal, T., Young, R.A. and Brown, S (1976) Function and structure in phage Q beta RNA replicase. Association of EF-Tu.Ts with the other enzyme subunits. J. Biol. Chem. 251, in press. Brown, S. and Blumenthal, T. (1976) Function and structure in ribonucleic acid phage Q beta ribonucleic acid replicase. Effect of inhibitors of EF-Tu on ribonucleic acid synthesis and renaturation of active enzyme. J. Biol. Chem. 251, in press.